1. Field of the Invention
Aspects of the invention relate to a battery pack, and more particularly, to a high power and high capacity battery pack including a plurality of unit batteries.
2. Description of the Related Art
Secondary batteries, unlike primary batteries, are rechargeable. Low capacity secondary batteries are used in small portable electronic devices, such as phones, notebook computers, and camcorders. High capacity secondary batteries are widely used as motor-driving power sources for hybrid vehicles. Such secondary batteries include cylinder type batteries and prismatic type batteries. A plurality of high power secondary batteries are connected in series to constitute a high capacity secondary battery, which is necessary to drive a motor of a device requiring high capacity, for example, a motor of an electric vehicle.
As such, a single high capacity secondary battery, i.e., a battery module, includes a plurality of unit batteries connected in series and/or in parallel. Each of the unit batteries includes an electrode assembly including a positive electrode plate and a negative electrode plate with a separator therebetween; a case in which the electrode assembly is disposed; a cap assembly coupled to the case to close the case; and positive and negative terminals that protrude from the cap assembly and are connected electrically to collectors of the positive and negative electrode plates of the electrode assembly. Thus, the unit batteries of the battery module are spaced apart from each other and connected in series and/or in parallel through electrode tabs. The battery module is inserted into a spacer to space the unit batteries apart from each other. Finally, the battery module is electrically connected to a protection circuit board and disposed in an outer case to provide a completed battery pack.
After being disposed in the outer case, the battery module of the battery pack may move in the outer case due to an external shock, so that the unit batteries may disconnect from each other or the protection circuit board. In an attempt to prevent such disconnection, a discrete gap prevention member is generally provided between the battery module and inner sidewalls of the outer case to prevent the battery module from moving in the outer case. However, since the discrete gap prevention member is added to the battery pack, manufacturing costs are increased. In addition, since it is difficult to assemble the discrete gap prevention member and the battery pack, productivity is decreased.
Alternatively, a discrete inner case may envelop the battery module and then be disposed in the outer case. However, since the battery pack still has a gap between the added inner case and the inner sidewalls of the outer case, it is difficult to prevent movement of the battery module.